Assessing threats and rehabilitation opportunities for mangrove-saltmarsh blue carbon ecosystems

Mangroves and salt marshes are vital intertidal ecosystems that provide key ecosystem services, including shoreline stabilization, carbon storage, and biodiversity support. This study assessed the current condition and threats to valued tidal wetland mangrove and saltmarsh ecosystems along the southern Great Barrier Reef (GBR) coastline, Queensland, Australia. The study also identified potential sites of rehabilitation potentially suitable for funding under Australia's blue carbon sequestration methodology. In 2023, an aerial shoreline survey was conducted between Gladstone and Cairns, revealing widespread impacts from climate-related stressors, such as shoreline erosion, expanding depositional banks and storm damage, along with anthropogenic stressors, including altered hydrology and agricultural encroachment. Fifty-two potential rehabilitation parcels totalling 17,255 ha were identified, with rehabilitation opportunities categorized as saltmarsh-dominated, mangrove-dominated, or mixed systems. Rehabilitation suitability was evaluated also using tidal barrier mapping, potential inundation extent, and trends in the normalized difference vegetation index (NDVI) of adjacent mangroves. The results revealed the importance of local stressors, the need for integrating stakeholder involvement, and the implementation of long-term environmental monitoring to bolster effective rehabilitation. This study provides a framework and baseline for selection and prioritizing rehabilitation efforts for improving the resilience and functionality of tidal wetlands in the GBR region. • Climatic stress responses dominated the threats along the southern GBR shoreline. • Other stressors included altered hydrology, agricultural encroachment, and pollution. • 52 rehabilitation sites identified, spanning 17,255 ha, with diverse ecosystem compositions. • Rehabilitation sites were evaluated for their potential suitability as blue carbon sequestration projects.